The Death and Resurrection of Jesus Christ is the central event in the history of world, and its celebration is the preeminent feast day in the Christian year. But not all Christians today—and not even all Orthodox Christians—celebrate this most holy Feast on the same day. Whatever one’s feelings about cooperation between communions, or “ecumenism,” the fact is that the division between Christian communions on the dating of Pascha is a stumbling block to non-believers and should be felt as a scandal to us all. This division and scandal is hardly a new problem, however.
In the earliest centuries of the Church, there were several possible ways to determine when Pascha could be celebrated (should it always be on March 25, the traditional date of the Crucifixion, or the Sunday after that? Or should it always be the Sunday after the Jewish Passover? Or should it not take into consideration the current Jewish calendar at all, and instead be calculated based on some different reckoning?).
Different local churches and traditions had different ways of determining and calculating the date of Pascha, and these differences and divisions were recognized to be scandalous even then. Which is why, at the Church’s first opportunity (the first council of Nicea), it decided—ecumenically—on one formulation for determining Pascha’s date: it would fall on the Sunday following the first full moon following the vernal equinox. The logic was that Jesus’ resurrection was certainly the first Sunday in Passover, and since Passover was meant to start in the Hebrew month of Nissan (which was supposed to be the first month of Spring), on the 14th day (always a full moon, since the Hebrew calendar was lunar), then the true beginning of Spring should be the vernal equinox, after which the first full moon would be the equivalent to the 14th of Nissan, after which the first Sunday would be the day of the Resurrection.
Simple. Now everyone agreed on when Pascha would be, and there was never another problem with it, and everyone lived happily ever after.
Except that we’re finite and fallible people—including those responsible for governing the Church—and there were two big problems baked into the Pascha dating solution. One was that it was really difficult 1700 years ago to determine when the vernal equinox and the following full moon would be very far in advance. So the Alexandrian church’s solution of artificially setting the “vernal equinox” to always fall on March 21 (regardless of when the astronomical equinox would be) was adopted, and a table of approximated future full moons and Paschal dates was published by Theophilus of Alexandria and adopted by the Church. Note: this was already an immediate departure from the spirit of the ecumenical decision. The second problem was that this computus was attached to the Julian Calendar, the only real contender of a calendar in use by the ecumene of the Roman Empire at the time, as it had a critical failure.
Though it was an improvement on the calendar which preceded it, Julius Caesar’s Calendar had a rigid leap year formula which gave it an average year of 365.25 days, while the solar reality is a year that’s approximately 365.2422 days long. That means it slips from the solar reality by one day about every 129 years. Several medieval and renaissance writers were aware of this drift, including St. Bede and Dante Alighieri. By the year 1582, the drift of the Julian Calendar from the solar reality had reached 10 days, and the Roman Catholic Church implemented a calendar reform to realign its calendar with the mean solar year (October 4 that year was followed by October 15).
The entire Western world would (relatively soon) holistically adopt this revised “Gregorian calendar” (named after Pope Gregory XIII, during whose pontificate the reform was enacted)—including eventually the nations of the Southern hemisphere which were under Western European influence—but the Eastern world had much less social, political, or religious incentive to adopt it. Only after the turn of the 20th century would the classically Eastern Orthodox nations adopt the updated calendar for their civil calendars, though most Orthodox ecclesiastical authorities steadfastly refused the change (intensifying thereby the religious/secular divide in those places).
At present, the Julian Calendar has now drifted 13 days behind the astronomical reality, but some local Orthodox churches have still refused to recalibrate their liturgical calendars at all; some have updated their calendars for everything but the Pashcal cycle; and a very few (including the Orthodox Church in Finland) use the updated calendar for the whole year, including the Paschal cycle.
“Aside from the one or two outliers among the Orthodox churches and jurisdictions,” some may wonder, “if the rest of the Orthodox are still celebrating Pascha together, what does it matter?” Without belaboring the scandal of all Christians failing at this most basic point of unity, even just among us Orthodox the use of the Julian Calendar and its computus is still a live problem. Every 129 years, when the Julian Calendar (and its computus using the artificial March 21 “equinox”) slips a day, Pascha might slip forward into the year by much longer, since Pascha would have to wait for the next full moon and then the next Sunday. Pascha used to fall no later than late April. Now it can fall within the second week of May (according to the civil calendar we all use). And it will continue to slip, eventually sliding solidly into Summer, even though Pascha is very clearly meant to be linked to Spring (in the Northern hemisphere).
When the best astronomers of the 4th century developed the computus to calculate the date of Pascha on their calendar (implemented, remember, by Julius Caesar 300 years before them), they were doing the best they could with what they had to adhere to Nicea I’s decision. In the 21st century, we have much more accurate tools of observation and calculation at our disposal (even more accurate than those used during Gregory XIII’s pontificate), and we can compute with extreme precision the dates of the March equinoxes and following full moons centuries in advance. We can now finally actually fulfill the first Ecumenical Council’s intended decision for when Pascha should be celebrated: on the Sunday following the first full moon following the vernal equinox.
Right now, the Orthodox Church is not adhering to that ecumenical decision. It should.
And the Western Rite of the Orthodox Church, with its ceremonies intended to strike chords of familiarity with our Western culture, has a uniquely strong incentive to advocate for an accurate calendar in order to provide its holy and beautiful services—of Shrove Tuesday, Ash Wednesday, Palm Sunday, Spy Wednesday, Maundy Thursday, Good Friday, Easter Sunday, the Holy Spirit Novena, a fiery red Pentecost, and Corpus Christi with its very public procession—to a culture looking for them when they expect them, and not a month or more later.
The simple solution to the convoluted problem of Orthodox Pascha’s current dating has already been worked out and proposed: we only have to use the astronomical equinox and full moon in order to comply exactly with the first Ecumenical Council’s dictate. Then the Orthodox Church at least, and whatever other Christian communions which so desire, would be celebrating our Lord’s victory over sin and death on the day which our saintly forebears intended and set forth for us.